ActionScript 3.0 :: Applying A Blurfilter To A Mask?

I have a sprite called MaskSprite, and another sprite called PhotoSprite, with this relationship:

PhotoSprite.mask = MaskSprite;

Now MaskSprite contains a bunch of sprites as children...basically, what I have is a bunch of rectangles spaced apart, so that only strips of PhotoSprite are revealed. This works fine. But I want to blur each of these individual child sprites...but the revealed parts of PhotoSprite aren't blurred in any way. Isn't it as simple as:

Code:

for(var i = 0; i < 10; i++){
var s = new Sprite();
MaskSprite.addChild(s);
s.graphics.drawRect(etc etc etc);
s.filters = [new BlurFilter(10,10,1)];